Noteworthy among a currency's characteristics is its ability to circulate and penetrate far beyond any barrier. A banknote can reach what no amount of propaganda can.
This is why one of its frequent uses in all wars is as a vehicle for propaganda, whether in its real format, by printing on legal-tender banknotes or in the form of imitations. One of the variants of this particular psychological warfare has been that of issuing safe-conducts that imitate local banknotes with the purpose of undermining the confidence of enemy troops and encourage defection.